U.S. patent application number 16/545406 was filed with the patent office on 2020-02-27 for power semiconductor device with reliably verifiable p-contact and method.
The applicant listed for this patent is Infineon Technologies Dresden GmbH & Co. KG. Invention is credited to Markus Beninger-Bina, Matteo Dainese, Ingo Dirnstorfer, Erich Griebl, Johannes Georg Laven, Anton Mauder, Hans-Joachim Schulze.
Application Number | 20200066579 16/545406 |
Document ID | / |
Family ID | 69412521 |
Filed Date | 2020-02-27 |
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United States Patent
Application |
20200066579 |
Kind Code |
A1 |
Beninger-Bina; Markus ; et
al. |
February 27, 2020 |
Power Semiconductor Device with Reliably Verifiable p-contact and
Method
Abstract
A method includes: forming trenches extending from a surface
along a vertical direction into a semiconductor body, facing trench
sidewalls of two adjacent trenches laterally confining a mesa
region of the semiconductor body along a first lateral direction;
forming a body region in the mesa region, a surface of the body
region in the mesa region at least partially forming the
semiconductor body surface; forming a first insulation layer on the
semiconductor body surface; subjecting the semiconductor body
region to a tilted source implantation using at least one contact
hole in the first insulation layer at least partially as a mask for
forming a semiconductor source region in the mesa region. The
tilted source implantation is tilted from the vertical direction by
an angle of at least 10.degree.. The semiconductor source region
extends for no more than 80% of a width of the mesa region along
the first lateral direction.
Inventors: |
Beninger-Bina; Markus;
(Grosshelfendorf, DE) ; Dainese; Matteo; (Munich,
DE) ; Dirnstorfer; Ingo; (Dresden, DE) ;
Griebl; Erich; (Dorfen, DE) ; Laven; Johannes
Georg; (Taufkirchen, DE) ; Mauder; Anton;
(Kolbermoor, DE) ; Schulze; Hans-Joachim;
(Taufkirchen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Infineon Technologies Dresden GmbH & Co. KG |
Dresden |
|
DE |
|
|
Family ID: |
69412521 |
Appl. No.: |
16/545406 |
Filed: |
August 20, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/32 20130101;
H01L 29/66674 20130101; H01L 29/66348 20130101; H01L 29/083
20130101; H01L 29/66727 20130101; H01L 29/7397 20130101; H01L
29/7801 20130101; H01L 29/41766 20130101; H01L 29/66734 20130101;
H01L 21/26586 20130101; H01L 29/404 20130101; H01L 21/31155
20130101; H01L 29/0696 20130101; H01L 29/0619 20130101; H01L 29/407
20130101; H01L 21/76816 20130101 |
International
Class: |
H01L 21/768 20060101
H01L021/768; H01L 29/66 20060101 H01L029/66; H01L 29/78 20060101
H01L029/78; H01L 29/739 20060101 H01L029/739; H01L 21/3115 20060101
H01L021/3115; H01L 21/32 20060101 H01L021/32 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 22, 2018 |
DE |
102018120432.9 |
Claims
1. A method of forming a power semiconductor device, the method
comprising: providing a semiconductor body having a surface;
forming a plurality of trenches extending from the surface along a
vertical direction into the semiconductor body, wherein two trench
sidewalls facing each other of two adjacent ones of the trenches
laterally confine a mesa region of the semiconductor body along a
first lateral direction; forming a semiconductor body region of a
second conductivity type in the mesa region, wherein a surface of
the semiconductor body region in the mesa region at least partially
forms the semiconductor body surface; forming a first insulation
layer on the semiconductor body surface, the first insulation layer
having at least one contact hole exposing at least a part of the
mesa region surface; subjecting the semiconductor body region of
the second conductivity type to a tilted source implantation using
the at least one contact hole at least partially as a mask for
forming a semiconductor source region of a first conductivity type
in the mesa region, wherein the tilted source implantation is
tilted from the vertical direction by an angle of at least
10.degree., and wherein the semiconductor source region extends for
no more than 80% of a width of the mesa region along the first
lateral direction.
2. The method of claim 1, further comprising: carrying out, after
forming the first insulation layer, a tilted body contact
implantation using the at least one contact hole at least partially
as a mask for forming a semiconductor body contact region of the
second conductivity type in the semiconductor body region, wherein
the tilted body contact implantation is tilted from the vertical
direction by an angle of at least 10.degree. and against the
tilting direction of the tilted source implantation.
3. The method of claim 1, wherein the tilted source implantation is
carried out such that the semiconductor source region is arranged
adjacent to only one of the two trench sidewalls and spatially
displaced along the first lateral direction from the other one of
the two trench sidewalls.
4. The method of claim 1, wherein the titled source implantation
comprises a first titled source implantation step and a second
titled source implantation step, the implantations being tilted
from the vertical direction by a respective angle of at least
10.degree. and against opposing tilting directions so as to form
semiconductor source regions adjacent to both trench sidewalls of
one of the two trenches.
5. The method of claim 4, further comprising: forming, before
carrying out the first and second tilted source implantation steps,
a resist block on a section of the insulation layer, the resist
block laterally overlapping with the one of the two adjacent
trenches, wherein the first and second tilted source implantation
steps are carried out so as to form semiconductor source regions
adjacent to both trench sidewalls of the trench that forms the
lateral overlap with the resist block.
6. The method of claim 4, wherein the first and second tilted
source implantation steps are tilted from the vertical direction by
a respective angle of at least 15.degree. and against opposing
tilting directions so as to form the semiconductor source regions
adjacent to both trench sidewalls of the one of the two trenches,
wherein a central subportion of the second conductivity type in the
mesa region is laterally displaced from the semiconductor source
region of the mesa region and forms a part of the mesa region
surface.
7. The method of claim 6, wherein the first and second tilted
source implantation steps are carried out so as to not subject the
central subportion of the mesa region to the first and second
tilted source implantation steps.
8. A method of forming a power semiconductor device, the method
comprising: providing a semiconductor body having a surface;
forming a plurality of trenches extending from the surface along a
vertical direction into the semiconductor body, wherein two trench
sidewalls facing each other of two adjacent ones of the trenches
laterally confine a mesa region of the semiconductor body along a
first lateral direction; forming a semiconductor body region of a
second conductivity type in the mesa region, wherein a surface of
the semiconductor body region in the mesa region at least partially
forms the semiconductor body surface; forming a first insulation
layer on the semiconductor body surface, the first insulation layer
having at least one contact hole exposing at least a part of the
mesa region surface; forming a resist layer comprising at least one
opening and at least one resist block, the at least one opening
partially exposing the mesa region surface, and the at least one
resist block partially covering the mesa region surface; subjecting
the semiconductor body region of the second conductivity type to a
source implantation along the vertical using the at least one
contact hole and the at least one resist block at least partially
as a mask for forming a semiconductor source region of a first
conductivity type in the mesa region, wherein the semiconductor
source region extends for no more than 80% of a width of the mesa
region along the first lateral direction.
9. The method of claim 8, further comprising: carrying out a body
implantation for forming the semiconductor body region in the mesa
region.
10. The method of claim 9, wherein the body implantation comprises
a first body implantation and a masked second body implantation,
the masked second body implantation being carried out with a higher
implantation dose as compared to the first body implantation.
11. The method of claim 10, wherein the source implantation is
carried out so as overdope the first body implantation and to not
overdope the masked second body implantation.
12. The method of claim 11, wherein the at least one contact hole
exposes a section of the mesa region surface that was covered by a
mask during the masked second body implantation.
13. The method of claim 10, wherein both the first body
implantation and the masked second body implantation are carried
out in parallel to the vertical direction and unmasked along the
entire width of the at least one contact hole along the first
lateral direction, and wherein the masked second body implantation
is masked along a length of the at least one contact hole in a
second lateral direction.
14. The method of claim 10, wherein both the first body
implantation and the masked second body implantation are carried
out in parallel to the vertical direction, and wherein the masked
second body implantation is masked along a length of the at least
one contact hole in a second lateral direction and along the width
of the at least one contact hole along the first lateral
direction.
15. The method of claim 10, wherein the body implantation comprises
a third body implantation for increasing the dopant concentration
of the semiconductor body region in a section of the mesa region
that is laterally displaced from the source region along the first
lateral direction.
16. The method of claim 10, wherein the first body implantation is
an unmasked implantation.
17. The method of claim 10, wherein formation of the semiconductor
body region by implantation is completed before the first
insulation layer is formed.
18. The method of claim 8, further comprising: forming a first load
terminal of the power semiconductor device by depositing an
electrically conductive material within the contact hole.
19. The method of claim 8, wherein the two adjacent trenches are
formed as: a control trench having a control electrode configured
to induce an inversion channel in the body region to control a load
current in the mesa region; and a source trench having a source
electrode.
20. The method of claim 8, further comprising: after forming the
first insulation layer and before carrying out the source
implantation, forming a laterally structured resist layer.
21. The method of claim 8, further comprising: after forming the
first insulation layer and before or after carrying out the source
implantation, forming a groove contact extending into the mesa
region along the vertical direction.
22. The method of claim 8, further comprising: after the source
implantation, subjecting the first insulation layer to a reflow
processing step.
23. The method of claim 8, wherein the first insulation layer has a
thickness along the vertical direction of at least 200 nm, and/or
wherein the first insulation layer comprises a plurality of
insulating sublayers, and/or wherein the first insulation layer is
made of a plurality of different insulating materials, and/or
wherein a width along the first lateral direction of the part of
the mesa region surface exposed by the at least one contact hole is
within a range of 50 nm to 500 nm.
24. A power semiconductor device having a semiconductor body, the
semiconductor body being coupled to a first load terminal and a
second load terminal and configured to conduct a load current
between the first and second load terminals, wherein the power
semiconductor device further comprises: a first trench and a second
trench that extend from a surface of the semiconductor body along a
vertical direction, the first and second trenches laterally
confining a mesa region along a first lateral direction; a
semiconductor source region of a first conductivity type and a
semiconductor body region of a second conductivity type both being
arranged in the mesa region adjacent to a trench sidewall of the
first trench and electrically connected to the first load terminal,
wherein the semiconductor source region is based on a first
implantation material, and wherein the first trench is configured
to induce an inversion channel in the body region to control a load
current in the mesa region; and a first insulation layer arranged
above the semiconductor body surface and having a plurality of
insulation blocks, two of which laterally confine a contact hole of
the first insulation layer, wherein the first load terminal extends
into the contact hole to contact both the semiconductor source
region and the semiconductor body region at a surface of the mesa
region, wherein a first of the two insulation blocks laterally
overlaps with the first trench and a second of the two insulation
blocks laterally overlaps with the second trench, wherein the first
insulation block has a first lateral concentration profile of the
first implantation material along the first lateral direction that
is different from a second lateral concentration profile of the
first implantation material along the first lateral direction
present in the second insulation block.
25. The power semiconductor device of claim 24, wherein the first
insulation block has a first concentration of the first
implantation material that is greater than a second concentration
of the first implantation material present in the second insulation
block, the first concentration being present in a section of the
first insulation block that laterally overlaps with the trench
sidewall of the first trench, and the second concentration being
present in a section of the second insulation block that laterally
overlaps with a trench sidewall of the second trench, the trench
sidewall laterally confining the mesa region.
Description
TECHNICAL FIELD
[0001] This specification refers to embodiments of a power
semiconductor device and to embodiments of a method of processing a
power semiconductor device. In particular, this specification
refers to aspects of a new body region formation process and to
corresponding devices.
BACKGROUND
[0002] Many functions of modern devices in automotive, consumer and
industrial applications, such as converting electrical energy and
driving an electric motor or an electric machine, rely on power
semiconductor switches. For example, Insulated Gate Bipolar
Transistors (IGBTs), Metal Oxide Semiconductor Field Effect
Transistors (MOSFETs) and diodes, to name a few, have been used for
various applications including, but not limited to switches in
power supplies and power converters.
[0003] A power semiconductor device usually comprises a
semiconductor body configured to conduct a load current along a
load current path between two load terminals of the device.
Further, the load current path may be controlled by means of an
insulated electrode, sometimes referred to as gate electrode. For
example, upon receiving a corresponding control signal from, e.g.,
a driver unit, the control electrode may set the power
semiconductor device in one of a conducting state and a blocking
state. In some cases, the gate electrode may be included within a
trench of the power semiconductor switch, wherein the trench may
exhibit, e.g., a stripe configuration or a needle
configuration.
[0004] It is usually desirable to keep losses, e.g., switching
losses, on-state losses during a conducting state and off-state
losses during a blocking state of the power semiconductor device
low.
[0005] Further, a power semiconductor device shall usually exhibit
a high reliability. To this end, it is desirable to check correct
manufacturing and/or proper functionality of the device before
shipping out to customers, and in particular to identify eventual
errors that may have occurred during manufacturing. For example,
those chips which are considered to exhibit a manufacturing error
are excluded from shipping out to customers.
[0006] Checking the correct manufacturing of the device may occur
at several stages. For example, at one stage, it may be checked
whether the semiconductor source and body regions have been
correctly formed within the semiconductor body and/or whether the
semiconductor source and body regions are correctly connected to
the load terminal of the device.
SUMMARY
[0007] Aspects described herein take into account the following
consideration: Although checking the correct manufacturing of a
power semiconductor device may occur at multiple stages during
manufacturing, defects caused by a single defect, e.g., during the
making of semiconductor source regions, can under circumstances not
reliably be detected during or after manufacturing on the wafer
level. Thus, it can be desirable to minimize the probability of
occurrence of such a defect by virtue of the device design. For
example, the manufacturing process can be modified such that two
defects need to occur on the same spot on the wafer at two
different times in the manufacturing process.
[0008] Further, aspects described herein relate to a new mesa
region formation process that allows for at least one of an
efficient check regarding the designated functionality of this
region and a highly reliable implementation of the designated
functionality of this region, in particular within the context of
semiconductor devices having a pattern trench structure according
to which trenches of different types (e.g. having different type of
electrodes, such as source and gate electrodes) are arranged
closely adjacent to each other on a regular basis. Such structure
may for example be implemented to form high efficient MOSFETs or
IGBTs, wherein said mesa region may include both a semiconductor
source region and a semiconductor body region of complementary
conductivity types and both connected to a source load terminal of
the device.
[0009] According to an embodiment, a method of forming a power
semiconductor device comprises: providing a semiconductor body
having a surface; forming a plurality of trenches, the trenches
extending from the surface along a vertical direction into the
semiconductor body, wherein two trench sidewalls facing to each
other of two adjacent ones of the trenches laterally confine a mesa
region of the semiconductor body along a first lateral direction;
forming a semiconductor body region of a second conductivity type
in the mesa region, wherein a surface of the semiconductor body
region in the mesa region at least partially forms the
semiconductor body surface; forming a first insulation layer on the
semiconductor body surface, the first insulation layer having at
least one contact hole exposing at least a part of the mesa region
surface; subjecting the semiconductor body region of the second
conductivity type to a tilted source implantation using the at
least one contact hole at least partially as a mask basis for
forming a semiconductor source region of a first conductivity type
in the mesa region, wherein the tilted source implantation is
tilted from the vertical direction by an angle of at least
10.degree., and wherein the formed semiconductor source region
extends for no more than 80% of the width of the mesa region along
the first lateral direction.
[0010] According to another embodiment, a method of forming a power
semiconductor device, comprises providing a semiconductor body
having a surface; forming a plurality of trenches, the trenches
extending from the surface along a vertical direction into the
semiconductor body, wherein two trench sidewalls facing to each
other of two adjacent ones of the trenches laterally confine a mesa
region of the semiconductor body along a first lateral direction;
forming a semiconductor body region of a second conductivity type
in the mesa region, wherein a surface of the semiconductor body
region in the mesa region at least partially forms the
semiconductor body surface; forming a first insulation layer on the
semiconductor body surface, the first insulation layer having at
least one contact hole exposing at least a part the mesa region
surface; forming a resist layer, the resist layer comprising at
least one opening and at least one resist block, the at least one
opening partially exposing the mesa region surface, and the at
least one resist block partially covering the mesa region surface;
subjecting the semiconductor body region of the second conductivity
type to a source implantation along the vertical direction using
the at least one contact hole and the at least one resist block at
least partially as a mask basis for forming a semiconductor source
region of a first conductivity type in the mesa region, wherein the
formed semiconductor source region extends for no more than 80% of
the width of the mesa region along the first lateral direction.
[0011] According to another embodiment, a power semiconductor
device is presented. The semiconductor device comprises a
semiconductor body, the semiconductor body being coupled to a first
load terminal and a second load terminal and configured to conduct
a load current between said terminals, wherein the power
semiconductor device further comprises: a first trench and a second
trench that extend from a surface of the semiconductor body along a
vertical direction, wherein the trenches laterally confine a mesa
region along a first lateral direction; a semiconductor source
region of a first conductivity type and a semiconductor body region
of a second conductivity type, both regions being arranged in the
mesa region adjacent to a trench sidewall of the first trench and
electrically connected to the first load terminal, wherein the
semiconductor source region is based on a first implantation
material, and wherein the first trench is configured for inducing
an inversion channel in the body region to control a load current
in the mesa region; a first insulation layer arranged above the
semiconductor body surface and having a plurality of insulation
blocks, two of which laterally confining a contact hole of the
first insulation layer, wherein the first load terminal extends
into the contact hole to contact both the semiconductor source
region and the semiconductor body region at a surface of the mesa
region, wherein a first of the two insulation blocks laterally
overlaps with the first trench and a second of the two insulation
blocks laterally overlaps with the second trench, the first
insulation block having a first lateral concentration profile of
the first implantation material along the first lateral direction
that is different from a second lateral concentration profile of
the first implantation material along the first lateral direction
present in the second insulation block.
[0012] Those skilled in the art will recognize additional features
and advantages upon reading the following detailed description, and
upon viewing the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The parts in the figures are not necessarily to scale,
instead emphasis is being placed upon illustrating principles of
the invention. Moreover, in the figures, like reference numerals
designate corresponding parts. In the drawings:
[0014] FIG. 1 schematically and exemplarily illustrates a section
of a vertical cross-section of a power semiconductor device at a
stage of a semiconductor device processing method in accordance
with one or more embodiments;
[0015] FIGS. 2-4 each schematically and exemplarily illustrate a
section of a horizontal projection of a power semiconductor device
at a stage of a semiconductor device processing method in
accordance one or more embodiments;
[0016] FIGS. 5-9 each schematically and exemplarily illustrate a
section of a vertical cross-section of a power semiconductor device
at a stage of a semiconductor device processing method in
accordance one or more embodiments;
[0017] FIGS. 10-11 each schematically and exemplarily illustrate a
section of a horizontal projection of a power semiconductor device
at a stage of a semiconductor device processing method in
accordance one or more embodiments;
[0018] FIG. 12-13 each schematically and exemplarily illustrate a
section of a vertical cross-section of a power semiconductor device
at a stage of a semiconductor device processing method in
accordance one or more embodiments;
[0019] FIGS. 14-15 each schematically and exemplarily illustrate a
section of a horizontal projection of a power semiconductor device
at a stage of a semiconductor device processing method in
accordance one or more embodiments;
[0020] FIG. 16 schematically and exemplarily illustrates stages of
a semiconductor device processing method in accordance with one or
more embodiments; and
[0021] FIG. 17A-17B each schematically and exemplarily illustrate a
section of a vertical cross-section of a power semiconductor device
in accordance with one or more embodiments; and
[0022] FIG. 18 schematically and exemplarily illustrates a section
of a vertical cross-section of a power semiconductor device at a
stage of a semiconductor device processing method in accordance
with one or more embodiments.
DETAILED DESCRIPTION
[0023] In the following detailed description, reference is made to
the accompanying drawings which form a part hereof and in which are
shown by way of illustration specific embodiments in which the
invention may be practiced.
[0024] In this regard, directional terminology, such as "top",
"bottom", "below", "front", "behind", "back", "leading",
"trailing", "above" etc., may be used with reference to the
orientation of the figures being described. Because parts of
embodiments can be positioned in a number of different
orientations, the directional terminology is used for purposes of
illustration and is in no way limiting. It is to be understood that
other embodiments may be utilized and structural or logical changes
may be made without departing from the scope of the present
invention. The following detailed description, therefore, is not to
be taken in a limiting sense, and the scope of the present
invention is defined by the appended claims.
[0025] Reference will now be made in detail to various embodiments,
one or more examples of which are illustrated in the figures. Each
example is provided by way of explanation, and is not meant as a
limitation of the invention. For example, features illustrated or
described as part of one embodiment can be used on or in
conjunction with other embodiments to yield yet a further
embodiment. It is intended that the present invention includes such
modifications and variations. The examples are described using
specific language which should not be construed as limiting the
scope of the appended claims. The drawings are not scaled and are
for illustrative purposes only. For clarity, the same elements or
manufacturing steps have been designated by the same references in
the different drawings if not stated otherwise.
[0026] The term "horizontal" as used in this specification intends
to describe an orientation substantially parallel to a horizontal
surface of a semiconductor substrate or of a semiconductor
structure. This can be for instance the surface of a semiconductor
wafer or a die or a chip. For example, both the first lateral
direction X and the second lateral direction Y mentioned below can
be horizontal directions, wherein the first lateral direction X and
the second lateral direction Y may be perpendicular to each
other.
[0027] The term "vertical" as used in this specification intends to
describe an orientation which is substantially arranged
perpendicular to the horizontal surface, i.e., parallel to the
normal direction of the surface of the semiconductor
wafer/chip/die. For example, the extension direction Z mentioned
below may be an extension direction that is perpendicular to both
the first lateral direction X and the second lateral direction Y.
The extension direction Z is also referred to as "vertical
direction Z" herein.
[0028] In this specification, n-doped is referred to as "first
conductivity type" while p-doped is referred to as "second
conductivity type". Alternatively, opposite doping relations can be
employed so that the first conductivity type can be p-doped and the
second conductivity type can be n-doped.
[0029] In the context of the present specification, the terms "in
ohmic contact", "in electric contact", "in ohmic connection", and
"electrically connected" intend to describe that there is a low
ohmic electric connection or low ohmic current path between two
regions, sections, zones, portions or parts of a semiconductor
device or between different terminals of one or more devices or
between a terminal or a metallization or an electrode and a portion
or part of a semiconductor device. Further, in the context of the
present specification, the term "in contact" intends to describe
that there is a direct physical connection between two elements of
the respective semiconductor device; e.g., a transition between two
elements being in contact with each other may not include a further
intermediate element or the like.
[0030] In addition, in the context of the present specification,
the term "electric insulation" is used, if not stated otherwise, in
the context of its general valid understanding and thus intends to
describe that two or more components are positioned separately from
each other and that there is no ohmic connection connecting those
components. However, components being electrically insulated from
each other may nevertheless be coupled to each other, for example
mechanically coupled and/or capacitively coupled and/or inductively
coupled. To give an example, two electrodes of a capacitor may be
electrically insulated from each other and, at the same time,
mechanically and capacitively coupled to each other, e.g., by means
of an insulation, e.g., a dielectric.
[0031] Specific embodiments described in this specification pertain
to, without being limited thereto, a power semiconductor switch
exhibiting a stripe cell or cellular cell configuration, e.g., a
power semiconductor device that may be used within a power
converter or a power supply. Thus, in an embodiment, such device
can be configured to carry a load current that is to be fed to a
load and/or, respectively, that is provided by a power source. For
example, the power semiconductor device may comprise one or more
active power semiconductor cells, such as a monolithically
integrated diode cell, e.g., monolithically integrated cell of two
anti-serially connected diodes, a monolithically integrated
transistor cell, e.g., a monolithically integrated IGBT cell and/or
derivatives thereof. Such diode/transistor cells may be integrated
in a power semiconductor module. A plurality of such cells may
constitute a cell field that is arranged with an active region of
the power semiconductor device.
[0032] The term "power semiconductor device" as used in this
specification intends to describe a semiconductor device on a
single chip with high voltage blocking and/or high current-carrying
capabilities. In other words, such power semiconductor device is
intended for high current, typically in the Ampere range, e.g., up
to several ten or hundred Ampere, and/or high voltages, typically
above 15 V, more typically 100 V and above, e.g., up to at least
400 V or even more, e.g., up to at least 3 kV, or even up to 10 kV
or more.
[0033] For example, the power semiconductor device described below
may be a semiconductor device exhibiting a stripe cell
configuration or a cellular (columnar/needle) cell configuration
and can be configured to be employed as a power component in a
low-, medium- and/or high voltage application.
[0034] For example, the term "power semiconductor device" as used
in this specification is not directed to logic semiconductor
devices that are used for, e.g., storing data, computing data
and/or other types of semiconductor-based data processing.
[0035] Each of FIG. 17A-B schematically and exemplarily illustrates
a power semiconductor device 1 in accordance with one or more
embodiments. In the following, it will be referred to both of FIGS.
17A and 17B.
[0036] The power semiconductor device 1 has a semiconductor body
10, the semiconductor body 10 being coupled to a first load
terminal 11 and a second load terminal 12 and configured to conduct
a load current between said terminals 11, 12.
[0037] For example, the power semiconductor device 1 has a MOSFET
configuration or an IGBT configuration or an RC-IGBT configuration
or a configuration derived from one of these basic power
semiconductor device configurations, such as an RC-IGBT with diode
control (RCDC) configuration. Hence, the first load terminal 11 can
be a source terminal or an emitter terminal, and the second load
terminal 12 can be a drain terminal or a collector terminal.
[0038] The power semiconductor device 1 may have a vertical
configuration, according to which the semiconductor body 10 is
sandwiched between the first load terminal 11 and the second load
terminal 12, and according to which the load current flows in a
direction essentially in parallel to the vertical direction Z.
[0039] Depending on the configuration of the power semiconductor
device 1, the semiconductor body 10 is provided with a plurality of
doped regions.
[0040] For example, the main part of the semiconductor body 10 is
formed by a drift region 1000 of the first conductivity type,
wherein the dopant concentration of the drift region 1000 is rather
low.
[0041] The drift region 1000 may be coupled to the second load
terminal 12 by means of a first doped region 108, which may
comprise a first emitter region of the second conductivity type
arranged in electrical contact with the second load terminal 12,
e.g., in case of an IGBT configuration. In addition, the first
doped region 108 may comprise second emitter regions of the first
conductivity type that are also arranged in electrical contact with
a second load terminal 12, e.g., so as to provide an RC-IGBT
configuration. In addition to at least one of the first emitter
region and the second emitter regions, the first contact region 108
may comprise a field stop region of the first conductivity type,
wherein the field stop region may have higher dopant concentration
of dopants of the first conductivity type as compared to the drift
region. In another embodiment, the first doped region 108 is
entirely a region of the first conductivity type, e.g. in case of a
MOSFET configuration. In the context of IGBTs, RC-IGBTs and
MOSFETs, the general functionality and configuration of the first
doped region 108 is known to the skilled person, and in accordance
with the embodiments described herein, is not deviated from this
general functionality and configuration of the first doped region
108.
[0042] In the section of the semiconductor body 10 that interfaces
with the first load terminal 11, a plurality of power cells may be
formed. For example, the power semiconductor device 1 includes a
plurality of equally configured power cells, e.g., at least 10,
100, or 1000 power cells, or at least 10,000 power cells or even
more than 100,000 power cells.
[0043] For example, each power cell includes a plurality of
trenches, e.g., at least one or more first trenches 14 and at least
one or more second trenches 15, each extending from a surface 100
of the semiconductor body 10 along the vertical direction Z,
wherein the trenches 14 and 15 laterally confine mesa regions 105
along the first lateral direction X.
[0044] The trenches 14 and 15 may exhibit a stripe configuration
according to which the lateral extension along the second lateral
direction Y is significantly larger than the total extension along
first lateral direction X, i.e., significantly larger than the
trench width. In an embodiment, the trenches of the power cells
each exhibit the same trench width (in the first lateral direction
X), the same trench depth (in the vertical direction Z) and are
spatially displaced from each other along the first lateral
direction X according to a fixed pattern.
[0045] The trench width may be defined as the distance between the
two trench sidewalls 144 (154, respectively) of each trench 14 (15,
respectively), and the trench depth may be defined as a distance
between the semiconductor body surface 100 and the trench bottom
145 (155, respectively).
[0046] Each trench 14, 15 may comprise a respective trench
electrode 141, 151 and a respective trench insulator 142, 152
insulating the trench electrodes 141, 152 from the semiconductor
body 10.
[0047] The above mentioned plurality of doped regions of the
semiconductor body 10 may include a semiconductor source region 101
of the first conductivity type and a semiconductor body region 102
of the second conductivity type, both regions 101, 102 being
arranged in at least one of the mesa regions 105 adjacent to the
trench sidewall 144 of the first trench 14 and electrically
connected to the first load terminal 11.
[0048] The semiconductor source region 101 typically, but not
necessarily, exhibits a significantly greater dopant concentration
as compared to the drift region 1000. The source region 101 is
arranged in electrical contact with the first load terminal 11. For
example, the semiconductor source region 101 forms a part of the
surface 100-5 of the mesa region 105 that interfaces with the first
load terminal 11. The first trench 14 may have semiconductor source
regions 101 arranged adjacent to both of its trench sidewalls 144,
or only one semiconductor source region 101 arranged adjacent to
only one of its trench sidewalls 144, which will become more
apparent from the subsequent description.
[0049] The semiconductor body region 102 (of the second
conductivity type) typically, but not necessarily, exhibits a
significantly greater dopant concentration as compared to the drift
region 1000, wherein the dopant concentration of the body region
102 may vary. For example, in a subsection of the body region 102
that interfaces with the first load terminal 11 may be stronger
doped as compared to another subsection of the body region 102, as
will be explained in more detail below. The body region is arranged
in electrical contact with the first load terminal 11. For example,
the semiconductor body region 102 also forms a part of the surface
100-5 of the mesa region 105 that interfaces with the first load
terminal 11. For example, the section of the semiconductor body
region 102 that interfaces with the first load terminal 11 has a
comparatively high dopant concentration as compared to the
remaining part of the semiconductor body region 102.
[0050] The semiconductor body region 102 may extend throughout the
entire width of the mesa region 105, as illustrated. The
semiconductor body region 102 isolates the semiconductor source
region 101 from the semiconductor drift region 1000. A transition
between the semiconductor body region 102 and the drift region 1000
forms the pn-junction 1025, wherein the pn-junction 1025 can be
arranged within the mesa regions 105.
[0051] The first trench 14 is configured for inducing an inversion
channel in the body region 102, e.g., in a subsection typically
called channel region, to control a load current in the mesa region
105. For example, the inversion channel is formed in the channel
region of the body region 102, wherein the channel region may be
arranged adjacent to the trench sidewall 144 and may extend below
the semiconductor source region 101.
[0052] By controlling the load current in each of the mesa regions
105 which have a configuration as just described (in particular:
both said source and body regions electrically connected to the
first load terminal 11), the load current of the power
semiconductor device 1 can be controlled. For example, the trench
electrode 141 of the first trench 14 is a gate electrode which
receives, from a driver (not illustrated), a gate signal, e.g.
formed by applying a voltage between a gate terminal (not
illustrated) and the first load terminal 11, wherein the gate
terminal may be electrically connected to the trench electrodes 141
of the first trenches 14.
[0053] Configurations of pn-isolations within mesa regions
laterally confined by trenches, as described above, are known to
the skilled person in the context of IGBTs, RC-IGBTs and MOSFETs,
and in accordance with the embodiments described herein, is not
deviated from this general functionality and configuration of such
pn-isolations.
[0054] Each power cell of the power semiconductor device 1 may
comprise more than only one mesa region 105, for example at least
two or three or four mesa regions 105 or even more than for mesa
regions 105, and a corresponding number of trenches. However, it
shall be understood that not each mesa region 105 of a respective
one of the power cells must be configured for conducting the load
current. Rather, in accordance with some embodiments, one or more
of the mesa regions 105 of the respective one of the power cells is
not configured for conducting the load current, wherein such
configuration may be achieved in different ways. For example, the
mesa region 105 is not configured for load current conduction if
not electrically connected to the first load terminal, as the
exemplary mesa region 105 between the two second trenches 15 in
FIG. 17A/B. Additionally or alternatively, the mesa region 105 is
not configured for load current conduction if not equipped with a
source region.
[0055] Further, with exemplary respect to the two mesa regions 105
arranged adjacent to the first trench 14 illustrated in FIG. 17A/B,
it shall be understood that along the second lateral direction Y,
the mesa region 105 may change its configuration regarding
capability of conducting the load current or not. For example, this
can be achieved by structuring the semiconductor source region 101
along the second lateral direction Y, which will become more
apparent from other drawings explained further below.
[0056] At least one of the second trenches 15, e.g., the second
trench 15 adjacent to the mesa region 105 including the source
region 101, can be a source trench whose trench electrode 151 is
electrically connected or at least electrically coupled to the
first load terminal 11.
[0057] One or more of the other second trenches 15 can, but must
not necessarily be different from both a source trench and a gate
trench. For example, further trench types may be provided for
forming the power cells, e.g., trenches with electrically floating
electrodes, trenches that have gate electrodes that are not
arranged adjacent to semiconductor source region (so-called dummy
gate trenches, herein also referred to as third trench 16, cf. FIG.
8) and the like.
[0058] Hence, in view of the explanation above regarding the
different configurations of the mesa regions and the trenches, the
power cells of the semiconductor device 1 may be configured in
accordance with various so-called contacting schemes, i.e., schemes
that define what type of trench is arranged adjacent to what type
of mesa region. However, in the context of IGBTs, RC-IGBTs and
MOSFETs, a plurality of different contacting schemes are known to
the skilled person, and the embodiments described herein are not
limited to specific contacting schemes, the contacting scheme for
example illustrated in FIG. 17A/B being only exemplary.
[0059] For example, in accordance with the embodiments described
herein, the load current conducting mesa region 105 is neighbored
by the first trench 14 implemented as a gate trench and by the
second trench 15 implemented as a source trench. If included, the
further second trenches 15 of each power cell may include one or
more of a dummy gate trench, a source trench and a floating
trench.
[0060] The semiconductor body surface 100 may be covered by a first
insulation layer 18 that has contact hole 185 so as to allow an
electrical connection between the first load terminal 11 and at
least some of the mesa regions 105. The contact holes 185 are
formed by respective two adjacent insulation blocks, namely for
example a first insulation block 181-1 above the first trench 14,
and two second insulation blocks 181-2 above the second trenches
15.
[0061] It shall be understood that the term "block" as used herein
does not imply any limitations regarding the geometrical shape of
the insulation (or resist, cf. below) blocks referred to. Rather,
the blocks referred to may, for example, be elements of a laterally
structured layer that appear as "blocks" in the illustrated
cross-sections.
[0062] The first insulation layer 18 can comprise or be composed of
various electrically insulating materials, e.g., mainly oxides. For
example, the first insulation layer 18 can comprise or be composed
an oxide and/or a low-k dielectric material. Further, the first
insulation layer 18 may exhibit a thickness along the vertical
direction Z of at least 200 nm, or of at least 400 nm, or of at
least 450 nm. The first insulation layer 18 may comprise a
plurality of (non-illustrated) insulating sublayers, e.g., a TEOS
(tetraethyl orthosilicate) or a spin on glass (e.g. BPSG, Boron
Phosphorus Silicate Glass) or another silicate glass sublayer. The
first insulation layer 18 can be made of a plurality of different
insulating materials, or of only one insulating material.
[0063] In an embodiment, the first insulation layer 18 is not an
auxiliary layer that would be removed during the device processing
methods; rather, the first insulation layer 18 remains a part of
the device, even during later operation of the device. For example,
the first insulation layer 18 is covered directly or indirectly
with an electrically conductive material, e.g., a metal, used for
forming the first load terminal 11 (wherein the first insulation
layer 18 may be covered with an additional insulation layer before
depositing the electrically conductive material).
[0064] The first insulation layer 18 is arranged above the
semiconductor body surface 100 and may have a plurality of said
insulation blocks 181, two of which laterally confining said at
least one contact hole 185 of the first insulation layer 18,
wherein the first load terminal 11 extends into the contact hole
185 to contact both the semiconductor source region 101 and the
semiconductor body region 102 at the surface 100-5 of the mesa
region 105. For example, the first insulation block 181-1 laterally
overlaps with the first trench 14 and the second insulation block
181-2 laterally overlaps with the second trench 15.
[0065] In an embodiment, a width along the first lateral direction
X of the part of the mesa region surface 100-5 exposed by the at
least one contact hole 185 (e.g., the width of the contact hole
185) is within the range of 50 nm to 2 .mu.m, for example in the
range of 50 nm to 250 nm or 250 nm to 550 nm or even 1 .mu.m to 2
.mu.m. The width may depend on the blocking voltage rating and/or
the load current capability of the power semiconductor device
1.
[0066] For example, as illustrated in FIG. 17A, the electrical
contact between the first load terminal 11 and the mesa region 105
can be realized as a flat contact which can be essentially arranged
co-planarily with the semiconductor body surface 100.
[0067] In another embodiment, as schematically and exemplarily
illustrated in FIG. 17B, the electrical contact between the first
load terminal 11 and the mesa region 105 can be realized by
employing a contact groove 111 that extends from the level of the
semiconductor body surface 100 along the vertical direction Z into
the mesa region 105. For example, such contact grooves 111 may be
etched into the semiconductor body 10 and later be filled with an
electrically conductive material.
[0068] If implemented, the contact groove 111 may extend further
into the semiconductor body 10 along the vertical direction Z than
the source region 101. The contact groove 111 may be etched, e.g.,
before or after forming the source region 101 by means of
implantation, as described further below.
[0069] The semiconductor source region 101 can be based on a first
implantation material or a group of first implantation materials.
The semiconductor body region 102 can be based on a second
implantation material or a group of second implantation materials.
Hence, for forming the semiconductor source region 101 and the
semiconductor body region 102, one or more implantation processing
steps may be carried out. The implantation processing steps may be
combined with one or more thermal diffusion steps (herein also
referred to as thermal annealing steps).
[0070] Aspects described herein relate to forming the mesa region
105 including the semiconductor source region 101 and the
semiconductor body region 102 by means of at least one implantation
processing step in a way that allows more reliably achieving a
proper electrical contact between the first load terminal 11 and
the mesa region 105 or, respectively, in a way that at least allows
a more reliable verification of a proper electrical contact between
the first load terminal 11 and the mesa region 105.
[0071] For example, according to an embodiment, a method of forming
a power semiconductor device comprises: providing a semiconductor
body having a surface; forming a plurality of trenches, the
trenches extending from the surface along a vertical direction into
the semiconductor body, wherein two trench sidewalls facing to each
other of two adjacent ones of the trenches laterally confine a mesa
region of the semiconductor body along a first lateral direction;
forming a semiconductor body region of a second conductivity type
in the mesa region, wherein a surface of the semiconductor body
region in the mesa region at least partially forms the
semiconductor body surface; forming a first insulation layer on the
semiconductor body surface, the first insulation layer having at
least one contact hole exposing at least a part of the mesa region
surface; subjecting the semiconductor body region of the second
conductivity type to a tilted source implantation using the at
least one contact hole at least partially as a mask basis for
forming a semiconductor source region of a first conductivity type
in the mesa region, wherein the tilted source implantation is
tilted from the vertical direction by an angle of at least
10.degree., and wherein the formed semiconductor source region
extends for no more than 80% of the width of the mesa region along
the first lateral direction.
[0072] For example, now referring to FIG. 1, providing the
semiconductor body 10 having the surface 100, and forming the
plurality of trenches 14, 15 may occur in the usual manner known to
skilled person. The semiconductor body 10 can be provided as a part
of a semiconductor wafer, and the trenches 14, 15 may be formed by
carrying out, for example, an etch processing step and a subsequent
oxidation processing step for forming the trench insulators 142,152
and a subsequent deposition processing step for forming the trench
electrodes 141, 151. This may be followed by another processing
step to recess the trench electrodes 141, 151 inside the respective
trench 14, 15 and form a further portion of the trench insulator
142, 152 on the recessed trench electrodes 141, 151.
[0073] Forming the semiconductor body region 102 of the second
conductivity type in the mesa region 105 may also involve standard
processes known to skilled person, such as a first blanket (i.e.,
not masked with respect to the mesa regions) implantation
processing step.
[0074] Optional features of forming the semiconductor body region
102 will be explained in more detail below. Irrespective of how the
semiconductor body region 102 is formed, in accordance with some or
all embodiments described herein and, before carrying out the next
processing steps, it can be ensured that the surface of the
semiconductor body region 102 in the mesa region 105 forms, at
least partially or entirely, the mesa region surface 100-5.
Further, it shall be noted that after it has been ensured that the
mesa region surface 100-5 is formed, partially or entirely, by the
semiconductor body region 102 of the second conductivity type,
further processing steps may be carried out at a later stage to
further modify the body region 102, e.g., by carrying out a masked
or unmasked contact implantation so as to provide for a high dopant
concentration of the body region 102 in a section that later
interfaces with the first load terminal 11 or, respectively, with
said contact groove 111.
[0075] As indicated above, the first insulation layer 18 is formed
on the semiconductor body surface 100, wherein the first insulation
layer 18 has the at least one contact hole 185 exposing, partially
or entirely, the mesa region surface 100-5 formed, partially or
entirely, by the body region 102.
[0076] Also, forming the first insulation layer 18 can be carried
out in accordance with standard processes known to the skilled
person (including, e.g., deposition and/or thermal oxidation
processing steps). For example, the first insulation layer 18 can
be or, respectively, comprise a dielectric interlayer.
[0077] As already indicated above, the first insulation layer 18
can comprise or be composed of various electrically insulating
materials, e.g., mainly oxides. For example, the first insulation
layer 18 can comprise or be composed an oxide and/or a low-k
dielectric material. Further, the first insulation layer 18 may
exhibit a thickness along the vertical direction Z of at least 200
nm, or of at least 400 nm, or of at least 450 nm. The first
insulation layer 18 may comprise a plurality of (non-illustrated)
insulating sublayers, e.g., a TEOS or a spin on glass (e.g. BPSG)
or another silicate glass sublayer. The first insulation layer 18
can be made of a plurality of different insulating materials, or of
only one insulating material.
[0078] After the first insulation layer 18 has been formed, the
semiconductor body region 102 of the second conductivity type is
subjected to a tilted source implantation 21 using the at least one
contact hole 185 at least partially as a mask basis for forming the
semiconductor source region 101 of the first conductivity type in
the mesa region 105, wherein the tilted source implantation 21 is
tilted from the vertical direction Z by an angle of at least
10.degree., as indicated in FIG. 1. This tilting angle can be even
greater than 10.degree., e.g., greater than 20.degree. or even
greater than 45.degree.. Further, the spatial extension area of the
semiconductor source region 101 may enlarge after an optional
temperature annealing processing step, e.g., such that the source
region 101 and the trench electrode 141 of the first trench 14 have
a common extension range along the vertical direction Z.
[0079] Further, it shall be understood that the formulation "using
the at least one contact hole 185 at least partially as a mask
basis" may imply that elements of the first insulation layer 18,
e.g., one or more insulation blocks 181, e.g., one or both of said
first insulation block 181-1 and said second insulation block 181-2
are used at least partially as a mask basis, wherein said at least
one insulation block 181, 181-1 or 182-2 laterally confines the at
least one contact hole 185.
[0080] As illustrated, the contact hole 185 or, respectively, at
least one of the blocks 181 laterally confining the contact hole,
can even serve as the mask itself, and not only as a mask basis. In
another embodiment (being described further below), the insulation
layer 18 may be partially covered by one or more further
components, e.g., a laterally structured resist layer, and in this
case, the insulation layer 18 with its contact hole 185 may serve
as the mask basis.
[0081] As becomes apparent from the illustration in FIG. 1, the
position (in terms of the first lateral direction X and the
vertical direction Z) and the form of the insulation layer contact
hole corner facing to the tilted implantation direction defines,
together with a tilting angle, where the source region 101 is
formed within the mesa region 105. For example, a higher insulation
layer contact hole corner shifts the right boundary of the source
region 101 to the left. A rounded corner would shift the right
boundary of the source region 101 to the left, and so on.
[0082] A first implantation material used during the source
implantation 21 for forming the semiconductor source region 101 may
include one or more of the following materials: arsenic (As),
antimony (Sb), selenium (Se), or phosphorus (P), or sulfur (S).
[0083] An implantation dose applied during the source implantation
21 for forming the semiconductor source region 101 may be within
the range of 1E14 cm.sup.-2 to 2E16 cm.sup.-2.
[0084] An implantation energy applied during the source
implantation 21 for forming the semiconductor source region 101 may
be within the range of 10 keV to 300 keV.
[0085] As indicated above, the tilting angle applied during the
source implantation 21 for forming the semiconductor source region
101 may be within the range of 10.degree. to 60.degree., wherein
the semiconductor wafer and/or the implantation device can be
tilted so as to achieve said tilting angle.
[0086] Irrespective of how the source implantation 21 for forming
the semiconductor source region 101 is carried out, it can be
ensured that the formed semiconductor source region 101 extends for
no more than 80% of the width of the mesa region 105 along the
first lateral direction X. For example, to this end, the tilted
source implantation 21 can be carried out such that the
semiconductor source region 101 is arranged adjacent to only one of
the two trench sidewalls 144 and spatially displaced along the
first lateral direction X from the other one of the two trench
sidewalls 154 of the trenches 14, 15 that laterally confine the
mesa region 105.
[0087] As illustrated in FIG. 1, the semiconductor source region
101 can for example be implemented only at one side of the mesa
region 105, e.g., within the section of the mesa region 105 that
interfaces with the first trench 14 (e.g., a gate trench). For
example, a distance between the right boundary of the semiconductor
source region 101 and the other trench 15 that laterally confines
the mesa region 105 amounts to at least 50 nm, to at least 200 nm
or to at least 500 nm. For example, this distance can be the
distance, along the first lateral direction X, between the trench
sidewall 154 of the second trench 15 and a substantially vertically
extending section of the pn-junction formed, adjacent to the
semiconductor body surface 100, between the semiconductor source
region 101 and the laterally adjacent section of the semiconductor
body region 102 (it shall be understood that, of course, said
pn-junction does not necessarily exhibit the strictly linear course
as schematically illustrated in FIG. 1).
[0088] In an embodiment, the mesa region 105, as also illustrated
in FIGS. 17A-B, has hence an asymmetrical design with respect to
the illustrated vertical cross-sections (being in parallel to the
plane defined by the first lateral direction X and the vertical
direction Z), according to which the interface between the first
load terminal 11 and the mesa region 105 is formed by both the
semiconductor body region 102 and the semiconductor source region
101.
[0089] Whereas the electron current of the load current of the
semiconductor device 1 is primarily conducted by sections of the
mesa region 105 that laterally overlap with the semiconductor
source regions 101, other types of currents, for example a hole
current, may at least primarily be conducted by exclusively the
body region 102 in the mesa region 105. Hence, it may be desirable
that both the semiconductor source region 101 and the semiconductor
body region 102 are properly electrically connected to the first
load terminal 11; in other words: it may be desirable that the mesa
region 105 is, with respect to the illustrated vertical
cross-sections (being in parallel to the plane defined by the first
lateral direction X and the vertical direction Z), well
electrically connected to the first load terminal 11 by an
interface formed by both the source region 101 and the body region
102, e.g., both a transition between the first load terminal 11 and
the source region 101 as well as a transition between the first
load terminal 11 and the body region 102 in said cross-section
should be low ohmic to provide for a good electrical contact.
[0090] For example, as indicated above and illustrated in FIG. 1,
formation the body region 102 may be continued after formation of
the first insulation layer 18. For example, similar to the source
implantation 21 for forming the source region 101, a body contact
implantation 22 can be carried out using the at least one contact
hole 185 at least partially as a mask basis for forming a
semiconductor body contact region 1021 of the second conductivity
type in the semiconductor body region 102, wherein the body contact
implantation 22 may be tilted from the vertical direction Z, e.g.,
by an angle of at least 10.degree. and against the tilting
direction of the tilted source implantation 21. The body contact
implantation 22 can be carried out before or after the tilted
source implantation 21. Further, as will become apparent from the
subsequent description, in another embodiment, formation of the
body region 102 including the body contact region 1021 may be
completed before forming the first insulation layer 18. For
example, in such embodiment, the first insulation layer 18 servers
as at least a mask basis only during application of the tilted
source implantation 21.
[0091] Now referring to FIG. 2, which schematically and exemplarily
illustrates a section of a horizontal projection the semiconductor
device 1 at a stage of a semiconductor device processing method in
accordance one or more embodiments, three contact holes 185 are
shown adjacent to two subsections of the first insulation layer 18
being arranged above the first trench 14 (e.g., a gate trench) and
the second trench 15 (e.g., a source trench), respectively.
[0092] Except for the body contact implantation 22 explained with
respect to FIG. 1, the semiconductor device processing method of
the embodiment shown in FIG. 2 may correspond to the embodiment
shown in FIG. 1. Hence, after the body regions 102 have been formed
in the mesa regions 105, e.g., by carrying out a blanket
implantation, the first insulation layer 18 is formed and
structured so as to produce the contact holes 185, and thereafter,
the tilted source implantation 21 is carried out so as to produce
the semiconductor source regions 101 in the mesa regions 105.
[0093] Thereafter, a masked body implantation can be carried out so
as to form the body contact regions 1021 within the body regions
102, said body contact regions 1021 having an increased dopant
concentration as compared to the remaining sections of the body
regions 102. The masked body implantation can be masked as
illustrated in FIG. 2, e.g., along the second lateral direction Y
and based on covering stripes 51 (illustrated by the dotted lines
along the vertical direction Z in FIG. 2) that extend along the
first lateral direction X and that are equidistantly spaced apart
from each other along the second lateral direction Y. Along these
stripes 51, the semiconductor source regions 101 and the sections
of the body regions 102 that have been previously formed are
covered and are hence not subjected to the masked body
implantation. The masked body implantation can be carried out so as
to in particular overdope the source regions 101 that have been
previously formed. Or, in another embodiment, the titled source
implantation 21 is also a masked implantation, using, e.g., a mask
complementary to the mask with stripes 51.
[0094] The sections of the body regions 102 that are covered by the
stripes 51 during said masked body implantation hence do not
exhibit the increased dopant concentration; these sections are
labeled with reference numeral 1022.
[0095] To further influence the position of the semiconductor
source regions 101, a resist layer may be formed above the first
insulation layer 18 before carrying out the tilted source
implantation 21, in accordance with some embodiments. This is
exemplarily and schematically illustrated in FIGS. 5 and 6.
[0096] Generally speaking, according to one or more embodiment, a
method of forming a power semiconductor device comprises providing
a semiconductor body having a surface; forming a plurality of
trenches, the trenches extending from the surface along a vertical
direction into the semiconductor body, wherein two trench sidewalls
facing to each other of two adjacent ones of the trenches laterally
confine a mesa region of the semiconductor body along a first
lateral direction; forming a semiconductor body region of a second
conductivity type in the mesa region, wherein a surface of the
semiconductor body region in the mesa region at least partially
forms the semiconductor body surface; forming a first insulation
layer on the semiconductor body surface, the first insulation layer
having at least one contact hole exposing at least a part the mesa
region surface. These steps can be carried out as exemplarily
described above.
[0097] Thereafter, the method may include forming a resist layer
19, the resist layer comprising at least one opening and at least
one resist block 191, the at least one opening partially exposing
the mesa region surface 100-5, and the at least one resist block
191 partially covering the mesa region surface 100-5 (cf. FIG. 6),
and subjecting the semiconductor body region 102 of the second
conductivity type to a source implantation along the vertical
direction Z using the at least one contact hole 185 and the at
least one resist block 191 at least partially as a mask basis for
forming the semiconductor source region 101 of the first
conductivity type in the mesa region 105, wherein the formed
semiconductor source region 101 extends for no more than 80% of the
width of the mesa region along the first lateral direction X.
Hence, since the resist block 191 may partially cover the mesa
region surface 100-5, it is not necessary that the source
implantation 21 is tilted, but the source implantation 21 can be
carried out along the vertical direction Z and still, it can be
achieved that the source region 101 extends for no more than 80% of
the width of the mesa region along the first lateral direction
X.
[0098] In another embodiment, the resist block 191 does not cover
the mesa region surface 100-5, but is arranged exclusively above
the first insulation layer 18, as exemplarily illustrated in FIG.
5.
[0099] In more general terms, the semiconductor device processing
method may hence include, after forming the first insulation layer
18 and before carrying out the source implantation 21, forming the
resist layer 19, wherein the resist layer 19 may be laterally
structured.
[0100] For example, referring to both FIG. 5 and FIG. 7, the titled
source implantation 21 may comprise a first titled source
implantation step 211 and a second titled source implantation step
212, the implantations 211, 212 being tilted from the vertical
direction Z by a respective angle of at least 10.degree. and
against opposing tilting directions so as to form semiconductor
source regions 101 adjacent to both trench sidewalls 144 of one of
the two trenches 14, e.g., adjacent to both trench sidewalls 144 of
the first trench 14 (e.g., the gate trench).
[0101] For example, in order to a) ensure that the semiconductor
source regions 101 are formed adjacent to both trench sidewalls 144
of the first trench 14, and b) that the both of the formed
semiconductor source regions 101 extend for no more than 80% of the
width of the respective mesa region 105 along the first lateral
direction X, several options exist.
[0102] In accordance with one option, as illustrated in FIG. 7, the
tilting angles are increased, e.g., up to more than 30.degree. or
even more than 45.degree. with respect to the vertical direction Z.
For example, the first and second source implantations 211, 212 are
carried out so as to not subject a central subportion of the second
conductivity type of the mesa region 105 to the two implantation
steps 211, 212, the central subportion in the mesa region 105 being
laterally displaced from the semiconductor source region (101) of
the mesa region 105 and forming a part of the mesa region surface
100-5. Rather, the above described body contact region 1021 may be
formed in this central subportion of the mesa region 105.
[0103] Another option is illustrated in FIG. 5, where the resist
block 191 ensures, at comparatively small tilting angles, that the
source regions 101 do not extend too far in or against the first
lateral direction X.
[0104] In accordance with yet another option, the source
implantation 21 is not tilted at all, but the resist blocks 191,
cover the mesa region surfaces 100-5 at least partially, as
illustrated in FIG. 6.
[0105] Further optional aspects of forming the semiconductor source
region 101 by subjecting the semiconductor body region 100 to the
tilted source implantation 21 using the contact hole 185 at least
as a mask basis will be described further below. The now following
explanation, which also refers to FIGS. 2-4, is directed to
optional aspects of forming the semiconductor body region 102 and
its body contact region 1021 that it may include.
[0106] As explained above, forming the semiconductor body region
102 may include one or more body implantations.
[0107] Additionally, in still general terms, each of the one or
more body implantations can occur along the vertical direction Z
(i.e., non-titled), or, one or more of the one or more body
implantations can be tilted. Further, each of the one or more body
implantations can occur unmasked with respect to the mesa regions
105, or, one or more of the one or more body implantations can be
masked with respect to the mesa regions 105.
[0108] In an embodiment, each of the one or more body implantations
is carried out before forming the first insulation layer 18. Hence,
forming the semiconductor body region 102 by means of the one or
more body implantations can be completed before forming the first
insulation layer 18, i.e., before forming the semiconductor source
region 101.
[0109] In another embodiment, forming the semiconductor body region
102 includes more than one body implantation, wherein a first body
implantation is carried out before forming the first insulation
layer 18 (and, hence, before forming the semiconductor source
region 101) and one or more subsequent second or third body
implantations are carried out after forming the first insulation
layer 18 (before and/or after the semiconductor source region 101
has been formed by means of the tilted source implantation 21).
[0110] For example, the body implantation comprises a first body
implantation and a masked second body implantation, the masked
second body implantation being carried out with a higher
implantation dose as compared to the first body implantation. Both
body implantations can be carried out along the vertical direction
Z. For example, the first body implantation is carried out so as to
form the body region 102 within the entire mesa regions 105. The
masked second body implantation can be carried out so as to form,
locally, the body contact regions 1021. For example, the first body
implantation is carried out before forming the first insulation
layer 18. The second masked body implantation can be carried out
after forming the first insulation layer 18 and, for example, also
after forming the semiconductor source regions 101. As indicated
above, the tilted source implantation 21 is carried out such that
body region 102 formed by means of the body implantation(s) is
overdoped in sections where the semiconductor source regions 101
are to be formed. For example, by means of the mask employed during
the second masked body implantation, the formed semiconductor
regions 101 are locally covered, as exemplarily illustrated in
FIGS. 3 and 4. The second masked body implantation can then be
carried out so as to overdope the semiconductor source regions 101
that are not covered by the mask, as illustrated in FIG. 3; or, in
another embodiment, such overdoping may be obsolete if the titled
source implantation 21 is also a correspondingly masked
implantation. In other words, the tilted source implantation does
not overdope those regions which are subjected to the masked second
body implantation, in accordance with an embodiment.
[0111] To ensure a good electrical contact between the
semiconductor source region 101 and the first load terminal 11, the
at least one contact hole 185 exposes a section of the mesa region
surface 100-5 that was covered by the mask during the masked second
body implantation. This is also schematically and exemplarily
illustrated in FIGS. 3 and 4, where the contact holes 185 of the
first insulation layer 18 expose each of the semiconductor source
regions 101 as well as the body contact regions 1021, e.g., the
entire surfaces 100-5 of the mesa regions 105.
[0112] As indicated above, it is possible that both the first body
implantation and the masked second body implantation are carried
out in parallel to the vertical direction Z, i.e., non-titled.
[0113] Both the first body implantation and the masked second body
implantation can occur unmasked along the entire width of the
(designated) contact hole 185 (depending on whether or not the
first insulation layer 18 has been formed) along the first lateral
direction X or, respectively, unmasked along the entire width of
the mesa region 105 along the first lateral direction X. The masked
second body implantation can be masked along a length of the
(designated) contact hole 185 in the second lateral direction Y,
or, respectively, masked along the length of the mesa region 105 in
the second lateral direction Y e.g., by means for said stripes 51
illustrated in FIG. 2.
[0114] In addition to being masked along the second lateral
direction Y, the masked second body implantation can also be
masked, with respect to the width of the mesa region 105, along the
first lateral direction X, as exemplarily and schematically
illustrated in FIG. 3. For example, the mask employed during the
second masked body implantation may cover entirely about 50% of the
width of the mesa region 105 adjacent to the second trench 15 that
laterally overlaps with the source regions 101 along the second
lateral direction, wherein said cover is indicated by the dotted
lines in FIG. 3.
[0115] Additionally in accordance with the embodiments described
with respect to FIG. 2 and FIG. 3, the body implantation may
comprise a third body implantation for increasing the dopant
concentration of the semiconductor body region 102 in a section
1023 of the mesa region 105 that is laterally displaced from the
(to be formed or already formed) source region(s) 101 along the
first lateral direction X. For example, this section 1023 laterally
overlaps with a stripe section of the mesa region 105 arranged
laterally adjacent to the second trench 15, as illustrated in FIG.
3.
[0116] As explained above, whereas the optional second and the
optional third body implantations can be masked implantations, the
first body implantation can be an unmasked implantation (also known
as "blanket" implantation), at least with regards to the active
area of the device 1 which includes the plurality of the power
cells and which may be surrounded by an edge termination area, as
it is known to the skilled person.
[0117] Further, as also explained above, at least one or all
implantations carried out for forming the body region 102
(including its optional body contact regions 1021 and its optional
highly doped sections 1023) can be completed before the first
insulation layer 18 is formed. For example, after formation of the
first insulation layer 18, no further implantation is carried out
to form or, respectively, modify the body region 102, in accordance
with an embodiment.
[0118] After the source regions 101 and the body regions 102 have
been completely formed, including optional temperature annealing
processing steps, the semiconductor device processing method may
further include forming the first load terminal 11 by depositing an
electrically conductive material within the contact holes 185,
e.g., so as to electrically contact each of the power cells of the
power semiconductor device 1. Specifically, by means of the contact
hole 185 filled with the electrically conductive material, both the
source region 101 and the body region 102 (including its body
contact region 1021) may be electrically contacted and the
electrical contact between the mesa region 105 and the first load
terminal 11 is established.
[0119] Further as has been explained above, the two adjacent
trenches 14 and 15 (of each power cell) can be formed as the
control (gate) trench 14 having the control (gate) electrode 141
configured for inducing the inversion channel in the body region
102 to control the load current in the mesa region 105, and as the
source trench 15 having the source electrode 151, e.g.,
electrically connected or at least coupled to the first load
terminal 11.
[0120] In addition, as has already been indicated with respect to
FIG. 17B, the power semiconductor device processing method may
further include, after forming the first insulation layer 18 and
before or after carrying out the source implantation 21, forming
the groove contact 111 extending into the mesa region 105 along the
vertical direction Z. For example, the semiconductor source region
101 is formed only adjacent to one side (with respect to the first
lateral direction X) of the groove contact 111, e.g., between the
first trench 14 and the groove contact 111, but not between the
groove contact 111 and the second trench 15.
[0121] Referring to all embodiments described herein, the power
semiconductor device processing method may further include
subjecting the first insulation layer 18 to a reflow processing
step. For example, the reflow processing step is carried out after
the source implantation 21 has been completed. For example, the
geometrical structure of the first insulation layer 18 is more
definite before the reflow processing step, and, hence, the
semiconductor source region 101 can be more accurately positioned
by means of the (titled) source implantation 21. In other
embodiments, the first insulation layer 18 may be specifically
modified with respect to the desired position of the semiconductor
source region 101.
[0122] With respect to FIGS. 8 to 15, aspects of further exemplary
embodiments shall be described, wherein these optional aspects
relate to use of the laterally structured resist layer 19 during
the source implantation 21 and to different types of contacting
schemes which may be employed for forming the power cells of the
power semiconductor device 1. The subsequent explanation is not
directed to the formation of the body region 102, wherein it shall
be understood that the body region 102 can be formed, also in
accordance with the embodiments illustrated in FIGS. 8 to 15, as
explained above.
[0123] For example, referring to FIG. 8, each power cell may
comprise two second trenches 15, and between these two second
trenches 15, two first trenches 14, and between the two first
trenches 14, a third trench 16. The third trench 16 can be, for
example, the above-mentioned dummy trench, i.e., comprise a trench
electrode (not illustrated) that is electrically connected to the
trench electrodes 141 of the first trenches 14, wherein the third
trench 16 is not capable of controlling a load current due to
absence of any source regions in its adjacent mesa regions 105. The
first insulation layer 18 may be formed and structured so as to
exhibit the contact holes 185 exposing only those mesa regions 105
that are laterally confined by one of the first trenches 14 and one
of the second trenches 15. The first insulation layer 18 can be
structured such that insulation blocks 181 cover the three central
trenches 14 and 16 as well as the two mesa regions 105 laterally
confined by these three trenches, and the two outer second trenches
15. In these mesa regions 105, the semiconductor source regions 101
are formed, e.g., by carrying out the first source implantation 211
and the second source implantation 212 that are tilted in opposing
tilting directions, as illustrated. Before the first source
implantation 211 and the second source implantation 212, the resist
block 191 is formed above the insulation block 181 so as to ensure
that during the tilted first implantation 211 and the tilted second
implantation 212, the corresponding semiconductor source regions
101 are spatially displaced from the respective second trench 15.
By means of choosing a height and/or a width (in the first lateral
direction X) of the resist block 191, the geometrical dimensions of
the source regions 101 may be influenced. For example, a resist
"pull-back", with respect to the underneath insulation block 181,
as indicated in FIG. 8, may lead to a lateral extension of the
source regions 101. At given tilting angles, it is clear to the
skilled person how a modification of the dimension of the resist
block 191 may influence the position of the source regions 101.
[0124] FIG. 10 exemplarily and schematically illustrates a section
of a horizontal projection of the embodiment shown in FIG. 8.
Hence, the resist layer 19 may be laterally structured such that
the resist block 191 is provided with optional resist block fingers
1912 that extend beyond the entire mesa regions 105 in which the
semiconductor source regions 101 are to be formed and even cover
the insulation blocks 181 that are arranged above the second
trenches 15. The resist block fingers 1912 may allow for the
lateral structure of the semiconductor source region 101 along the
second lateral direction Y.
[0125] With reference to FIGS. 9 and 11, another contacting scheme
is presented. For example, each power cell comprises three second
trenches 15 and one first trench 14 and is configured in such a way
that the first trenches 14 are neighbored by two second trenches
15, the third second trench 15 being arranged adjacent to one of
the neighboring two second trenches 15. Both mesa regions 105
arranged adjacent to the first trench 14 are equipped with a
respective source region 101. In order to form the source regions
101, it may generally be proceeded as described above, hence, by
forming the first insulation layer 18 including the insulation
blocks 181 defining the contact holes 185, and by forming the
laterally structured resist layer 19 with the plurality of resist
blocks 191. Those mesa regions 105 which shall not be electrically
connected to the first load terminal 11 (not illustrated in FIG. 9)
may be entirely covered by one of the resist blocks 191, as
schematically and exemplarily illustrated in FIG. 9. Also in
accordance with the embodiment illustrated by FIGS. 9 and 11, the
source regions 101 may be formed by carrying out the first tilted
source implantation 211 and the second tilted source implantation
212. By means of the height of the relevant resist blocks 191 and
by means of their lateral extensions (along the first lateral
direction X), the positions of the semiconductor source regions 101
may be defined. Of course, regarding the position of the source
regions 101 at given tilting angles, also the height of the first
insulation layer 18 is relevant, as has been explained above.
[0126] FIG. 11 schematically and exemplarily shows a section of a
horizontal projection of the embodiment shown in FIG. 9,
illustrating in particular the lateral structure of the resist
layer 19 and its resist block(s) 191. In FIG. 11, those parts of
the resist block 191 which are visible also in FIG. 9 are labelled
with the reference numeral 191. Similar to the embodiment
illustrated in FIGS. 8 and 10, by means of the optional resist
fingers 1912, the source regions 101 may be laterally structured
along the second lateral direction Y.
[0127] Hence, the lateral structure of the resist layer 19 does not
only influence the position of the source region 101 in terms of
the first lateral direction X, but may also be used in order to
structure the source regions 101 along the second lateral direction
Y, in accordance with some embodiments.
[0128] FIGS. 12 and 14 illustrate a slight modification to the
embodiment shown in FIGS. 8 and 10, and FIGS. 13 and 15 illustrate
a slight modification to the embodiment shown in FIGS. 9 and 11. As
explained above, producing the source regions 101 with limited
lateral extension (e.g., no more than 80% of the width of the mesa
region 105 along the first lateral direction X) does not
necessarily involve carrying out a tilted source implantation, but
the source implantation 21 can occur along the vertical direction
Z, if, for example, the resist blocks 191 partially cover the mesa
region surface 100-5. Hence, as has already been explained with
respect to FIG. 6, the sections of the mesa regions 105 covered by
the resist blocks 191 are not subjected to the source implantation
21, and hence, the semiconductor source regions 101 will
substantially not extend into these mesa sections. The remaining
description of FIGS. 8 to 11 may analogously apply to the
embodiments of FIGS. 12 and 14 as well as FIGS. 13 and 15,
respectively.
[0129] The following, it will be referred to FIG. 16 (which extends
over drawing sheets 9 and 10) for explaining an exemplary process
flow of an embodiment of the power semiconductor device processing
method. In the left part of FIG. 16, a respective section of a
vertical cross-section of the semiconductor device during a
specific processing stage is illustrated, and the right part of
FIG. 16 shows a section of a horizontal projection.
[0130] At processing stage (a), the semiconductor body 10 has been
provided, the trenches 14 and 15 have been formed, including the
trench electrodes 141, 151 and the trench insulators 142, 152, and
the semiconductor body region 102 has been formed, e.g., by
carrying out a blanket implantation, e.g. The above-mentioned first
body implantation. Further, a first temperature annealing
processing step has been carried out so as to cause healing and
diffusion of the implanted material used for forming the body
region 102.
[0131] Processing stages (b) and (c) are directed to further
forming the body region 102, while taking into account the
designated position of the source regions 101 to be formed.
[0132] For example, at stage (b), a laterally structured resist
layer 30 is deposited on the semiconductor body surface 100, e.g.,
so as to partially cover the first trench 14 as well as the
surfaces 100-5 of its adjacent mesa regions 105. The resist layer
30 can be structured along the second lateral direction Y, e.g., by
laterally displaced stripe sections 301, as schematically
illustrated in the right part of stage (b). Then, the
above-mentioned masked second body implantation can be carried out,
using the laterally structured resist layer 30 as a mask
(illustrated only in the left part of stage (b), not in the right
part of stage (b)). This implantation may lead to preliminary body
contact regions 1021-1. The preliminary body contact regions 1021-1
come hence into being in sections of the mesa regions 105 which are
not covered by the resist layer 30. Further, it is understandable
already at this point, that the laterally structured resist layer
30 used as a mask during the second body implantation covers those
sections of the mesa regions 105 where the semiconductor source
regions 101 are to be produced.
[0133] For example, at stage (c), which is optional, a further
masked body implantation may be carried out. This further masked
body implantation may be carried out using the same laterally
structured resist layer 30 as during stage (b), as illustrated in
the left part of stage (c), or using a different laterally
structured mask 31, as illustrated in the right part of stage (c).
When using the laterally structured mask 31 different from the
laterally structured mask 30, it can be ensured that those sections
of the mesa regions 105 covered by the laterally structured mask 30
are also covered by the other laterally structured mask 31, as
illustrated in the right part of stage (c).
[0134] In any case, the result of processing stages (a) and (b) and
the optional processing stage (c) includes the body region 102 and
the body contact regions 1021.
[0135] The next processing stages (d) and (e) are directed to
forming the semiconductor source regions 101:
[0136] For example, within the scope of stage (d), the resist
layer(s) used for forming the body region 102 are removed. After
the removal of the resist layer(s), the first insulation layer 18
may be formed, which may include an oxide deposition processing
step and subsequent etch processing step, yielding the insulation
blocks 181 which define the contact holes 185. Regarding the right
part of stage (d), it becomes apparent that the mesa region
surfaces 100-5 are entirely formed by the body region 102, wherein,
depending on the previously used resist layers, the dopant
concentration may laterally vary along the mesa region surfaces
100-5. For example, reference numeral 1021 illustrates the highly
doped body contact region. Reference numeral 1022 indicates those
sections of the body region 102 that were covered by the resist
layer 30, specifically: the stripe sections 301, used during the
processing stage (b). The parts of the body region 102 which are
not labeled with a reference numeral in the right part of
processing stage (d) either have the same dopant concentration as
the regions 1022, namely if the resist layer 30 is not changed at
processing stage (c). However, if the other resist layer 31 is used
during processing stage (c) (as illustrated in the right part of
stage (c)), then the non-labeled sections of the body region 102
would not become subjected to the third body implantation, and
would hence exhibit a dopant concentration higher than the dopant
concentration of regions 1022, but lower than the dopant
concentration of region 1021.
[0137] Hence, the contact holes 185, which may extend stripe like
according to the mesa regions 105, may expose the mesa region
surfaces 100-5 that are formed by sections of the body region 102
having different dopant concentrations.
[0138] At processing stage (e), the mesa region surfaces 100-5 are
subjected to the tilted source implantation so as to form the
semiconductor source regions 101. As explained above, the source
implantation may include the first tilted source implantation 211
and, optionally, the second tilted source implantation 212 so as to
form the semiconductor source regions 101 adjacent to only one side
of the first trench 14 or, as illustrated, so as to form the
semiconductor source regions 101 adjacent to both sides of the
first trench 14. Whether or not the second tilted source
implantation 212 is carried out may depend on the desired final
design of the power cells of the power semiconductor design, e.g.,
on the desired contacting scheme. Forming the source region(s) 101
may or may not include forming, before carrying out the source
implantation, the resist layer 19 including the resist block 191,
as explained above. Whether or not the resist layer 19 is necessary
may depend on the total height of the first insulation layer 18
and/or the chosen tilting angles.
[0139] Due to the tilted source implantations 211 and 212, the
stripe like body contact regions 1021 are substantially not
subjected to the implantations, but rather only the sections of the
body region 102 indicated with reference numeral 1022 and the
adjacent non-labeled sections (as illustrated in the right part of
stage (d)). The tilted source implantations 211 and 212 overdope at
least sections 1022, such that at least there the semiconductor
source regions 101 of the first conductivity type come into being.
For example, the tilted source implantations 211 and 212 are
carried out so as to not overdope the non-labelled sections,
leading to weekly doped sections 1024 of the second conductivity
type. Hence, it shall be understood that even though the first
insulation layer 18 may not be structured along the second lateral
direction Y, by choosing corresponding resist layers during
formation of the body region 102 and by choosing corresponding
implantation energies/doses during formation of the body region 102
and the source region 101, the source region 101 may be laterally
structured along the second lateral direction Y.
[0140] After the source region 101 has been formed, the resist
layer 19 (if used at all) may be removed. Other processing steps,
which are not illustrated, may include one or more thermal
processing steps to get the implantation material used for the
source region 101 and/or the implantation material used for the
channel region 102 electrically activated.
[0141] Of course, the herein proposed method may include further
processing steps so as to complete manufacturing of the power
semiconductor device 1, which may, as explained above, finally
exhibit a MOSFET configuration or an IGBT configuration or an
RC-IGBT configuration or a configuration derived from one of these
basic power semiconductor device configurations, such as an RC-IGBT
with diode control (RCDC) configuration. For example, such further
processing steps may be carried out so as to form the first and
second load terminals 11 and 12, e.g., by deposition of
metallizations. The further processing steps may further include
forming the first doped region, e.g., by means of implantation.
[0142] An optional effect that may come into being due to forming
the semiconductor source regions 101 by means of the two tilted
source implantations 211 and 212 is indicated by the crosshatched
and dotted regions at the insulation blocks 181. As it is apparent
from the foregoing description, vertical flanks of the insulation
block 181 that covers the first trench 14 are substantially
entirely subjected to the two implantations 211 and 212 (dotted
area). In contrast, the vertical flanks of the two insulation
blocks 181 that cover the second trenches 15 are only partially
subjected to the two tilted implantations 211 and 212 (crosshatched
area). Thus, each of the three insulation blocks 181 may exhibit a
concentration of the implantation material used for forming the
semiconductor source regions 101, wherein the concentration profile
of the implantation material may differ between the insulation
blocks 181.
[0143] Hence, in accordance with an embodiment and now referring to
FIGS. 17A-B again, presented herein is also a power semiconductor
device 1 having the following features: [0144] a semiconductor body
10, the semiconductor body 10 being coupled to a first load
terminal 11 and a second load terminal 12 and configured to conduct
a load current between said terminals 11, 12; [0145] a first trench
14 and a second trench 15 that extend from a surface 100 of the
semiconductor body 10 along a vertical direction Z, wherein the
trenches 14, 15 laterally confine a mesa region 105 along the first
lateral direction X; [0146] a semiconductor source region 101 of
the first conductivity type and a semiconductor body region 102 of
the second conductivity type, both regions 101, 102 being arranged
in the mesa region 105 adjacent to a trench sidewall 144 of the
first trench 14 and electrically connected to the first load
terminal 11, wherein the semiconductor source region 101 is based
on a first implantation material, and wherein the first trench 14
is configured for inducing an inversion channel in the body region
102 to control a load current in the mesa region 105; [0147] a
first insulation layer 18 arranged above the semiconductor body
surface 100 and having a plurality of insulation blocks 181, two of
which laterally confining a contact hole 185 of the first
insulation layer 18, wherein the first load terminal 11 extends
into the contact hole 185 to contact both the semiconductor source
region 101 and the semiconductor body region 102 at a surface 100-5
of the mesa region 105, wherein a first of the two insulation
blocks 181-1 laterally overlaps with the first trench 14 and a
second of the two insulation blocks 181-2 laterally overlaps with
the second trench 15, the first insulation block 181-1 having a
first lateral concentration profile of the first implantation
material along the first lateral direction X that is different from
a second lateral concentration profile of the first implantation
material along the first lateral direction X present in the second
insulation block 181-2.
[0148] For example, based on the explanation of the left part of
stage (e) of FIG. 16, the first insulation block 181-1 (i.e., the
insulation block that covers the first trench 14 in FIG. 17A/B) has
a first concentration of the first implantation material that is
greater than a second concentration of the first implantation
material present in the second insulation block 181-2 (i.e., the
insulation block that covers one of the second trenches 15 in FIG.
17A/B), the first concentration being present in a section of the
first insulation block 181-1 that laterally overlaps with the
trench sidewall 144 of the first trench 14 (cf. dotted areas of
insulation block 181-1), and the second concentration being present
in a section of the second insulation block 181-2 that laterally
overlaps with a trench sidewall 154 of the second trench 15 (cf.
cross-hatched areas in the second insulation blocks 181-2), said
trench sidewall 154 laterally confining the mesa region 105.
[0149] For example, said first concentration of the first
implantation material in the relevant section of the first
insulation block 181-1 is at least twice as great as said second
concentration of the first implantation material and the relevant
section of a second insulation block 181-2. For example, the first
concentration and the second concentration of dopants are
determined at the same position with respect to the second lateral
direction Y and the vertical direction Z.
[0150] Regarding all embodiments described herein, some further
optional aspects are described in the following:
[0151] For example, regarding the optional resist layer 19 that may
be used during formation of the semiconductor source region 101,
and, in particular, the resist block 191 arranged on top of the
insulation block 181 that covers the first trench 14 adjacent to
which the semiconductor source regions 101 shall be formed, it
shall be noted that the resist block 191 may exhibit a height along
the vertical direction Z of at least 500 nm, or of at least 1 .mu.m
or of even more than 1.5 .mu.m. The resist block 191 may exhibit a
width along the first lateral direction X which is substantially
identical to the width of the insulation block 181 arranged
underneath the resist block 191. As has been explained above, the
width of the resist block 191 and the height of the resist block
191 may be modified so as to influence the position of the
semiconductor source region(s) 101. For example, the resist
material may be "pulled back", leading to a width of the resist
block 191 which is slightly smaller than the width of the
underlying insulation block 181, e.g. smaller by up to 200 nm as
compared to the width of the underneath insulation block 181. The
resist block 191 may in another embodiment exhibit a width slightly
greater as compared to the underlying insulation block 181.
[0152] Referring to FIG. 18, some exemplary dimensions of an
embodiment of the power semiconductor device 1 are presented.
[0153] For example, the width WM of the mesa region 105, e.g.,
defined as the distance along the first lateral direction X between
the two trench sidewalls 144, 154 that laterally confine the mesa
region 105, e.g. measured at a vertical level where also the source
region 101 (not illustrated in FIG. 18) is present, can be within
the range of some hundred nm, e.g., wider than 100 nm and smaller
than 5 .mu.m, or within the range of 300 nm to 2 .mu.m, e.g.,
within the range of 400 nm to 1400 nm, such as approximately 600 nm
to 800 nm.
[0154] The width WH of the contact hole 185 defined by the
insulation blocks 181 of the first insulation layer 18 can be about
the same size as the mesa width WM, e.g., slightly smaller as the
mesa width WM. Hence, the insulation blocks 181 may laterally
overlap with the trench insulators 142/152 of the underneath
trenches 14/15 and even cover small sections of the mesa region
surface 100-5. The contact hole width WH may for example the
approximate 450 nm if the mesa width WM amounts to 600 nm.
[0155] In the above, embodiments pertaining to power semiconductor
switches and corresponding processing methods were explained. For
example, these semiconductor devices are based on silicon (Si).
Accordingly, a monocrystalline semiconductor region or layer, e.g.,
the semiconductor body 10 and its regions/zones, e.g., regions etc.
can be a monocrystalline Si-region or Si-layer. In other
embodiments, polycrystalline or amorphous silicon may be
employed.
[0156] It should, however, be understood that the semiconductor
body 10 and its regions/zones can be made of any semiconductor
material suitable for manufacturing a semiconductor device.
Examples of such materials include, without being limited thereto,
elementary semiconductor materials such as silicon (Si) or
germanium (Ge), group IV compound semiconductor materials such as
silicon carbide (SiC) or silicon germanium (SiGe), binary, ternary
or quaternary III-V semiconductor materials such as gallium nitride
(GaN), gallium arsenide (GaAs), gallium phosphide (GaP), indium
phosphide (InP), indium gallium phosphide (InGaPa), aluminum
gallium nitride (AlGaN), aluminum indium nitride (AlInN), indium
gallium nitride (InGaN), aluminum gallium indium nitride (AlGalnN)
or indium gallium arsenide phosphide (InGaAsP), and binary or
ternary II-VI semiconductor materials such as cadmium telluride
(CdTe) and mercury cadmium telluride (HgCdTe) to name few. The
aforementioned semiconductor materials are also referred to as
"homojunction semiconductor materials". When combining two
different semiconductor materials a heterojunction semiconductor
material is formed. Examples of heterojunction semiconductor
materials include, without being limited thereto, aluminum gallium
nitride (AlGaN)-aluminum gallium indium nitride (AlGalnN), indium
gallium nitride (InGaN)-aluminum gallium indium nitride (AlGalnN),
indium gallium nitride (InGaN)-gallium nitride (GaN), aluminum
gallium nitride (AlGaN)-gallium nitride (GaN), indium gallium
nitride (InGaN)-aluminum gallium nitride (AlGaN), silicon-silicon
carbide (SixC1-x) and silicon-SiGe heterojunction semiconductor
materials. For power semiconductor switchs applications currently
mainly Si, SiC, GaAs and GaN materials are used.
[0157] Spatially relative terms such as "under", "below", "lower",
"over", "upper" and the like, are used for ease of description to
explain the positioning of one element relative to a second
element. These terms are intended to encompass different
orientations of the respective device in addition to different
orientations than those depicted in the figures. Further, terms
such as "first", "second", and the like, are also used to describe
various elements, regions, sections, etc. and are also not intended
to be limiting. Like terms refer to like elements throughout the
description.
[0158] As used herein, the terms "having", "containing",
"including", "comprising", "exhibiting" and the like are open ended
terms that indicate the presence of stated elements or features,
but do not preclude additional elements or features.
[0159] With the above range of variations and applications in mind,
it should be understood that the present invention is not limited
by the foregoing description, nor is it limited by the accompanying
drawings. Instead, the present invention is limited only by the
following claims and their legal equivalents.
* * * * *